Computer rooms and other building spaces intended for specialized uses often require precise control and regulation of environmental conditions such as temperature and humidity in order to ensure proper operation of equipment (such as but not limited to computers) installed in such building spaces. Cooling requirements for computer rooms are typically much greater and more stringent than for most building spaces due to the need to dissipate heat generated by the computer equipment operating in the computer rooms. Humidity control requirements are typically stringent as well, as excessive moisture in the air in a computer room can cause operational and maintenance problems with the computer equipment.
Accordingly, computer rooms commonly are provided with specialized air conditioning (A/C) systems for controlling and regulating temperature and humidity. It has been common in the past for computer room A/C systems to be located outside the computer room and even outside the building housing the computer room, due to the physical size of the equipment needed to meet the A/C requirements for the computer room in question. In recent years, however, computer room air conditioning units (or “CRAC units”) have been developed that are sufficiently compact for installation within a computer room without greatly increasing the required floor area or height of the computer room. Examples of such CRAC units include chilled water or DX (direct expansion) A/C units manufactured by the Liebert® Corporation.
Conventional CRAC units commonly utilize banked (i.e., angularly-oriented) cooling coils specially constructed for use in CRAC unit and arrayed in an A-frame or V-frame configuration within the unit. Airflow typically enters the unit vertically through the top or bottom of the unit and proceeds in a straight, vertical path through the filters and coils. In CRAC units of this type, the air velocity through the filters (also referred to herein as the “face velocity”) is comparatively high, which results in reduced filter performance.
Another drawback of known CRAC units is that they cannot be readily adapted to use direct evaporative cooling systems using saturated evaporative media pads without increasing the size of the units so much that their use within a computer room becomes unviable or undesirable. Direct evaporative cooling systems using saturated evaporative media pads rely on gravity to allow water sprayed on top of the unit to trickle down, saturating the pad through which the airstream passing through the CRAC unit travels. Some of the water in the evaporative pad evaporates into the airstream, adiabatically cooling it. Water is collected in a sump located beneath the evaporative pad. However, this type of direct evaporative cooling system cannot be used in conventional CRAC units using a conventional vertical airflow pattern, because the evaporative media pads would have to be oriented horizontally, such that water would not be able to drain from the media by gravity into a drain pan. Moreover, the requirement for the evaporative media to be horizontally oriented for use in a CRAC unit having a vertical airflow pattern would increase the size of the unit and the floor area it requires.
For the foregoing reasons, there is a need for CRAC units characterized by lower face velocities (and therefore better filter performance and efficiency) than conventional CRAC units, without increasing the physical size of the units significantly or at all. In addition, there is a need for CRAC units that can be adapted to use direct evaporative cooling media, without significant effect on the physical size of the units.